feat: submodularize qw; streamline stress/run qw

This commit soft-depends on:
- crawl/qw#2 for Depths being four levels deep
- crawl/qw#3 for armour switching behavior with the slot rename
- crawl/qw#4 for automatic ("streamlined") starting

This commit depends on crawl/qw#2 for Depths being four levels deep,
soft-depends on crawl/qw#3 for proper armour switching behavior due to
the slot rename, as well as crawl/qw#4 for automatic starting.

Author: perryprog

.gitmodules

@@ -31,3 +31,6 @@
 [submodule "crawl-ref/source/contrib/sdl2-mixer"]
 	path = crawl-ref/source/contrib/sdl2-mixer
 	url = https://github.com/crawl/crawl-sdl2-mixer.git
+[submodule "crawl-ref/source/test/stress/qw"]
+	path = crawl-ref/source/test/stress/qw
+	url = https://github.com/crawl/qw.git